/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.kie.internal.services;

import java.util.HashMap;
import java.util.Map;
import java.util.ServiceLoader;

public abstract class AbstractMultiService<K, V> {

    private volatile Map<K, V> servicesMap;

    protected V getService(K key) {
        if (servicesMap == null) {
            init();
        }
        return servicesMap.get(key);
    }

    private synchronized void init() {
        if (servicesMap == null) {
            servicesMap = new HashMap<>();
            ServiceLoader<V> loader = ServiceLoader.load(serviceClass());
            for (V service : loader) {
                servicesMap.put(serviceKey(service), service);
            }
        }
    }

    protected abstract Class<V> serviceClass();

    protected abstract K serviceKey(V service);
}
